Dog ownership is associated with higher physical activity levels in adults; whether this association occurs in children is unknown. We used accelerometry to examine physical activity levels in 2065 children aged 9 to 10 years. Children from dog-owning families spent more time in light or moderate to vigorous physical activity and recorded higher levels of activity counts per minute (25; 95% confidence interval [CI]=6, 44) and steps per day (357; 95% CI=14, 701) than did children without dogs.